[PP] Replace some index based for loops with range based ones

[erikjv]

Summary

While in the area, also change some unsigned variables to size_t, and
introduce an LLVM_FALLTHROUGH instead of a comment stating that.

[bkramer]

lib/Lex/PPLexerChange.cpp

43

This wasn't a reverse loop?

Also I think at this point writing it with none_of is more readable:

return std::none_of(IncludeMacroStack.begin() + 1, IncludeMacroStack.end(), IsFileLexer);

[bkramer]

lgtm

lib/Lex/PPCaching.cpp

void Preprocessor::EnterCachingLexMode() {
   PushIncludeMacroStack();
   CurLexerKind = CLK_CachingLexer;
 }
 
 
 const Token &Preprocessor::PeekAhead(unsigned N) {
   assert(CachedLexPos + N > CachedTokens.size() && "Confused caching.");
   ExitCachingLexMode();
-  for (unsigned C = CachedLexPos + N - CachedTokens.size(); C > 0; --C) {
+  for (size_t C = CachedLexPos + N - CachedTokens.size(); C > 0; --C) {
     CachedTokens.push_back(Token());
     Lex(CachedTokens.back());
   }
   EnterCachingLexMode();
   return CachedTokens.back();
 }
 
 void Preprocessor::AnnotatePreviousCachedTokens(const Token &Tok) {

lib/Lex/PPLexerChange.cpp

 /// \#include.  This looks through macro expansions and active _Pragma lexers.
 bool Preprocessor::isInPrimaryFile() const {
   if (IsFileLexer())
     return IncludeMacroStack.empty();
 
   // If there are any stacked lexers, we're in a #include.
   assert(IsFileLexer(IncludeMacroStack[0]) &&
          "Top level include stack isn't our primary lexer?");
-  for (unsigned i = 1, e = IncludeMacroStack.size(); i != e; ++i)
-    if (IsFileLexer(IncludeMacroStack[i]))
+  for (const IncludeStackInfo &ISI : llvm::reverse(
+         llvm::make_range(IncludeMacroStack.begin() + 1,
+                          IncludeMacroStack.end())))
+    if (IsFileLexer(ISI))
       return false;
   return true;
 }
 
 /// getCurrentLexer - Return the current file lexer being lexed from.  Note
 /// that this ignores any potentially active macro expansions and _Pragma
 /// expansions going on at the time.
 PreprocessorLexer *Preprocessor::getCurrentFileLexer() const {
   if (IsFileLexer())
     return CurPPLexer;
 
   // Look for a stacked lexer.
-  for (unsigned i = IncludeMacroStack.size(); i != 0; --i) {
-    const IncludeStackInfo& ISI = IncludeMacroStack[i-1];
+  for (const IncludeStackInfo &ISI : llvm::reverse(IncludeMacroStack)) {
     if (IsFileLexer(ISI))
       return ISI.ThePPLexer;
   }
   return nullptr;
 }
 
 
 //===----------------------------------------------------------------------===//

 void Preprocessor::HandleMicrosoftCommentPaste(Token &Tok) {
   assert(CurTokenLexer && !CurPPLexer &&
          "Pasted comment can only be formed from macro");
   // We handle this by scanning for the closest real lexer, switching it to
   // raw mode and preprocessor mode.  This will cause it to return \n as an
   // explicit EOD token.
   PreprocessorLexer *FoundLexer = nullptr;
   bool LexerWasInPPMode = false;
-  for (unsigned i = 0, e = IncludeMacroStack.size(); i != e; ++i) {
-    IncludeStackInfo &ISI = *(IncludeMacroStack.end()-i-1);
+  for (const IncludeStackInfo &ISI : llvm::reverse(IncludeMacroStack)) {
     if (ISI.ThePPLexer == nullptr) continue;  // Scan for a real lexer.
 
     // Once we find a real lexer, mark it as raw mode (disabling macro
     // expansions) and preprocessor mode (return EOD).  We know that the lexer
     // was *not* in raw mode before, because the macro that the comment came
     // from was expanded.  However, it could have already been in preprocessor
     // mode (#if COMMENT) in which case we have to return it to that mode and
     // return EOD.

lib/Lex/PPMacroExpansion.cpp

else
     Val = CurTokenLexer->isNextTokenLParen();
 
   if (Val == 2) {
     // We have run off the end.  If it's a source file we don't
     // examine enclosing ones (C99 5.1.1.2p4).  Otherwise walk up the
     // macro stack.
     if (CurPPLexer)
       return false;
-    for (unsigned i = IncludeMacroStack.size(); i != 0; --i) {
-      IncludeStackInfo &Entry = IncludeMacroStack[i-1];
+    for (const IncludeStackInfo &Entry : llvm::reverse(IncludeMacroStack)) {
       if (Entry.TheLexer)
         Val = Entry.TheLexer->isNextPPTokenLParen();
       else if (Entry.ThePTHLexer)
         Val = Entry.ThePTHLexer->isNextPPTokenLParen();
       else
         Val = Entry.TheTokenLexer->isNextTokenLParen();
 
       if (Val != 2)
if (InMacroArgs) {
       // reading the function macro arguments. To ensure, in that case, that
       // MacroExpands callbacks still happen in source order, queue this
       // callback to have it happen after the function macro callback.
       DelayedMacroExpandsCallbacks.push_back(
           MacroExpandsInfo(Identifier, M, ExpansionRange));
     } else {
       Callbacks->MacroExpands(Identifier, M, ExpansionRange, Args);
       if (!DelayedMacroExpandsCallbacks.empty()) {
-        for (unsigned i = 0, e = DelayedMacroExpandsCallbacks.size(); i != e;
-             ++i) {
-          MacroExpandsInfo &Info = DelayedMacroExpandsCallbacks[i];
+        for (const MacroExpandsInfo &Info : DelayedMacroExpandsCallbacks) {
           // FIXME: We lose macro args info with delayed callback.
           Callbacks->MacroExpands(Info.Tok, Info.MD, Info.Range,
                                   /*Args=*/nullptr);
         }
         DelayedMacroExpandsCallbacks.clear();
       }
     }
   }
MacroArgs *Preprocessor::ReadFunctionLikeMacroArgs(Token &MacroName,
   unsigned NumActuals = 0;
   while (Tok.isNot(tok::r_paren)) {
     if (ContainsCodeCompletionTok && Tok.isOneOf(tok::eof, tok::eod))
       break;
 
     assert(Tok.isOneOf(tok::l_paren, tok::comma) &&
            "only expect argument separators here");
 
-    unsigned ArgTokenStart = ArgTokens.size();
+    size_t ArgTokenStart = ArgTokens.size();
     SourceLocation ArgStartLoc = Tok.getLocation();
 
     // C99 6.10.3p11: Keep track of the number of l_parens we have seen.  Note
     // that we already consumed the first one.
     unsigned NumParens = 0;
 
     while (true) {
       // Read arguments as unexpanded tokens.  This avoids issues, e.g., where
Token *Preprocessor::cacheMacroExpandedTokens(TokenLexer *tokLexer,
   size_t newIndex = MacroExpandedTokens.size();
   bool cacheNeedsToGrow = tokens.size() >
                       MacroExpandedTokens.capacity()-MacroExpandedTokens.size(); 
   MacroExpandedTokens.append(tokens.begin(), tokens.end());
 
   if (cacheNeedsToGrow) {
     // Go through all the TokenLexers whose 'Tokens' pointer points in the
     // buffer and update the pointers to the (potential) new buffer array.
-    for (unsigned i = 0, e = MacroExpandingLexersStack.size(); i != e; ++i) {
+    for (const auto &Lexer : MacroExpandingLexersStack) {
       TokenLexer *prevLexer;
       size_t tokIndex;
-      std::tie(prevLexer, tokIndex) = MacroExpandingLexersStack[i];
+      std::tie(prevLexer, tokIndex) = Lexer;
       prevLexer->Tokens = MacroExpandedTokens.data() + tokIndex;
     }
   }
 
   MacroExpandingLexersStack.push_back(std::make_pair(tokLexer, newIndex));
   return MacroExpandedTokens.data() + newIndex;
 }
 

lib/Lex/Pragma.cpp

if (StrVal[0] == 'R') {
     StrVal.erase(0, 2 + NumDChars);
     StrVal.erase(StrVal.size() - 1 - NumDChars);
   } else {
     assert(StrVal[0] == '"' && StrVal[StrVal.size()-1] == '"' &&
            "Invalid string token!");
 
     // Remove escaped quotes and escapes.
     unsigned ResultPos = 1;
-    for (unsigned i = 1, e = StrVal.size() - 1; i != e; ++i) {
+    for (size_t i = 1, e = StrVal.size() - 1; i != e; ++i) {
       // Skip escapes.  \\ -> '\' and \" -> '"'.
       if (StrVal[i] == '\\' && i + 1 < e &&
           (StrVal[i + 1] == '\\' || StrVal[i + 1] == '"'))
         ++i;
       StrVal[ResultPos++] = StrVal[i];
     }
     StrVal.erase(StrVal.begin() + ResultPos, StrVal.end() - 1);
   }

lib/Lex/TokenConcatenation.cpp

case tok::utf32_char_constant:
     // single token.
     if (Tok.getIdentifierInfo())
       return true;
 
     // A ud-suffix is an identifier. If the previous token ends with one, treat
     // it as an identifier.
     if (!PrevTok.hasUDSuffix())
       return false;
-    // FALL THROUGH.
+    LLVM_FALLTHROUGH;
   case tok::identifier:   // id+id or id+number or id+L"foo".
     // id+'.'... will not append.
     if (Tok.is(tok::numeric_constant))
       return GetFirstChar(PP, Tok) != '.';
 
     if (Tok.getIdentifierInfo() ||
         Tok.isOneOf(tok::wide_string_literal, tok::utf8_string_literal,
                     tok::utf16_string_literal, tok::utf32_string_literal,

lib/Lex/TokenLexer.cpp

if (!PasteBefore && !PasteAfter) {
       const Token *ArgTok = ActualArgs->getUnexpArgument(ArgNo);
       if (ActualArgs->ArgNeedsPreexpansion(ArgTok, PP))
         ResultArgToks = &ActualArgs->getPreExpArgument(ArgNo, Macro, PP)[0];
       else
         ResultArgToks = ArgTok;  // Use non-preexpanded tokens.
 
       // If the arg token expanded into anything, append it.
       if (ResultArgToks->isNot(tok::eof)) {
-        unsigned FirstResult = ResultToks.size();
+        size_t FirstResult = ResultToks.size();
         unsigned NumToks = MacroArgs::getArgLength(ResultArgToks);
         ResultToks.append(ResultArgToks, ResultArgToks+NumToks);
 
         // In Microsoft-compatibility mode, we follow MSVC's preprocessing
         // behavior by not considering single commas from nested macro
         // expansions as argument separators. Set a flag on the token so we can
         // test for this later when the macro expansion is processed.
         if (PP.getLangOpts().MSVCCompat && NumToks == 1 &&
             ResultToks.back().is(tok::comma))
           ResultToks.back().setFlag(Token::IgnoredComma);
 
         // If the '##' came from expanding an argument, turn it into 'unknown'
         // to avoid pasting.
-        for (unsigned i = FirstResult, e = ResultToks.size(); i != e; ++i) {
-          Token &Tok = ResultToks[i];
+        for (Token &Tok : llvm::make_range(ResultToks.begin() + FirstResult,
+                                           ResultToks.end())) {
           if (Tok.is(tok::hashhash))
             Tok.setKind(tok::unknown);
         }
 
         if(ExpandLocStart.isValid()) {
           updateLocForMacroArgTokens(CurTok.getLocation(),
                                      ResultToks.begin()+FirstResult,
                                      ResultToks.end());
if (NumToks) {  // Not an empty argument?
         // Remove the paste operator, report use of the extension.
         PP.Diag(ResultToks.pop_back_val().getLocation(), diag::ext_paste_comma);
       }
 
       ResultToks.append(ArgToks, ArgToks+NumToks);
 
       // If the '##' came from expanding an argument, turn it into 'unknown'
       // to avoid pasting.
-      for (unsigned i = ResultToks.size() - NumToks, e = ResultToks.size();
-             i != e; ++i) {
-        Token &Tok = ResultToks[i];
+      for (Token &Tok : llvm::make_range(ResultToks.end() - NumToks,
+                                         ResultToks.end())) {
         if (Tok.is(tok::hashhash))
           Tok.setKind(tok::unknown);
       }
 
       if (ExpandLocStart.isValid()) {
         updateLocForMacroArgTokens(CurTok.getLocation(),
                                    ResultToks.end()-NumToks, ResultToks.end());
       }